Device for metering fuel

ABSTRACT

A device is described for metering fuel in internal combustion engines is provided, which includes a fuel distributor provided with a flow channel and at least one discharge orifice connected thereto, a valve which is connected to the fuel distributor for metering the fuel and has a pipe connection that is able to be attached to the discharge orifice, and connection means, which connects the fuel distributor and the valve to each other in the attachment region of the pipe connection and the discharge orifice in a pressure-tight manner.

FIELD OF THE INVENTION

The present invention is based on a device for metering fuel in internalcombustion engines according to the definition of the species in claim1. In this case, fuel describes a fluid, i.e., a liquid or gaseous fuel,whose chemical energy is transformed into a driving force through acombustion in an internal combustion engine, such as an Otto engine, aDiesel engine or a gas engine.

BACKGROUND INFORMATION

In one known device for fuel injection in internal combustion engines(German Patent No. 197 58 817 B4), a connection cup, which encloses theconnection opening, is premolded on the fuel distributor, and anintermediate sleeve having an intake section is inserted into theconnection cup and sealed from the cup wall with the aid of an O-ring.The intermediate sleeve is fixed in place on the fuel distributor by asecuring element that engages with the intermediate sleeve and theconnection cup in a form-fitting manner Via its pipe connection, thevalve for metering the fuel is inserted into a widened section of theintermediate sleeve and sealed from the sleeve wall by an O-ring. Aseparate spring mount, between which a pressure spring is braced, isformed on the fuel distributor and the valve. After the valve has beeninserted into a cylinder head bore in the cylinder head of the internalcombustion engine and after the fuel distributor is secured on thecylinder head, the pressure spring, which is tensioned during theassembly, retains the valve with force-locking inside the cylinder bore.

SUMMARY

The device according to the present invention has the advantage ofproducing a seal between the valve and fuel distributor in theattachment region of the pipe connection and upstream flow opening,which seals in a reliable manner even at extremely high pressures andhas a long service life. By positioning the flange element, whichgenerates the contact pressure between the connection head and seatsurface at the discharge opening, in the receiving element fixed inplace on the valve, the at least one clamping bolt secured on the fueldistributor is able to “blindly” find the threaded hole during theassembly, so that the assembly can be simplified and automated.Optionally, a preassembly of the valves and the fuel distributor, or aninstallation of the fuel distributor on the valves already in place inthe cylinder head of the internal combustion engine is able to takeplace. Once the fuel distributor and the valves are assembled, theflange element secured on the fuel distributor by the at least oneclamping bolt clamps the connection head to the seat surface at the fueldistributor, so that the receiving head is unstressed. As a result, thereceiving element will not have to satisfy special conditions in termsof stability.

According to one advantageous embodiment of the present invention, theflange element is a flat part and the receiving element has at least onebearing surface for the flat flange element and multiple detent hooksthat overlap the flange element. Each detent hook has an integrallypremolded hook strip, which axially projects from the at least onebearing surface, as well as a detent, which projects inwardly from thehook strip and overlaps the flange element on the side facing away fromthe bearing surface. The detent hooks not only fixate the flange elementon the valve but also allow an axial tolerance compensation betweenflange element and undercut at the connection head once the fueldistributor and valve are assembled.

According to one advantageous specific embodiment of the presentinvention, a keyed connection that positions the flange element existsbetween the hook strips and the flange element. This keyed connectionensures the positionally precise alignment of the at least one threadedhole in the flange element in relation to the at least one clamping bolton the fuel distributor.

Valves for metering fuel typically have a valve housing, which is sealedby a connector piece that is inserted into the valve housing at theextremity and integrally connected thereto. The connector piece has anintake bore, which connects the pipe connection to a fluid duct providedinside the valve housing, which in turn discharges into a valve chamberupstream from a metering orifice of the valve. In a first version, thepipe connection is inserted as a separate component into a blind hole inthe connector and fixed in place by a plastic extrusion coat on theconnector and the valve housing. In a second version of the valve, thepipe connection is integrally formed with the connector.

In one specific embodiment of the present invention that is adapted tothe first version of the valve, the flange element is developed inmirror symmetry with the valve axis and has a central through hole forthe pipe connection, and two diametrically positioned threaded holes; apressure surface which engages with the undercut of the connection headis formed in the through hole. The flange element is already taken intoaccount during the valve assembly and slipped over the pipe connectionbefore the pipe connection is inserted into the connector and fixed inplace on the connector and the valve housing by the plastic extrusioncoat. During the extrusion coating, the receiving element is extruded atthe same time.

In one specific embodiment of the present invention, which is adapted tothe second version of the valve, the flange element is developed in theshape of a fork which has two fork arms that reach over the pipeconnection and include a contact surface that engages with the undercutof the connection head in each case, and a fork back, which connects thefork arms to each other and has a machined threaded hole. The receivingelement is provided with three separate seat surfaces, for the fork backand one end each of the two fork arms, as well as three detent hooks,one of which overlaps the fork back and an end of the two fork arms ineach case. In this constructive development, it is possible to place theflange element on top of the pipe connection in the finished valveretroactively, prior to producing the receiving element with the aid ofthe plastic extrusion coating. In addition, it is also possible to lockor clip the flange element into place in the receiving element producedby the plastic extrusion coating on the finished valve.

According to one advantageous specific embodiment of the presentinvention, the seat surface at the valve opening and the head surface atthe connection head are made of metal. Such a metal-to-metal connectionrequiring a high contact pressure between connection head and seatsurface makes it possible to reduce the hydrocarbon emissions in theexhaust gas. The high contact pressure is produced by means of at leastone clamping bolt.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a device for metering fluid, depicted in a cutaway view.

FIG. 2 a plan view of a flange element, accommodated in a receivingelement, in the device according to FIG. 1.

FIG. 3 a longitudinal section of the device according to a secondspecific embodiment, in a cutaway view.

FIG. 4 a plan view of a flange element, situated inside a receivingelement, in the device according to FIG. 3.

DETAILED DESCRIPTION

The device for metering fluid, shown in the form of a cutaway view as alongitudinal section in FIG. 1, for example, is used for the injectionof fuel into the combustion chamber of an internal combustion engine.The fuel is under a very high system pressure. The device includes afuel distributor 11 and a valve 12 for metering the fuel, which isconnected to a fuel distributor 11. Fuel distributor 11 has a flowchannel 13 and at least one discharge orifice, 14 which is in connectionwith flow channel 13. As a rule, a plurality of discharge orifices 14are provided for multiple valves 12, but for reasons of clarity only asingle discharge orifice 14 is shown in FIG. 1.

Valve 12 has a pipe connection 15 to connect valve 12 to dischargeorifice 14. Pipe connection 15 is form-fittingly inserted into a blindhole 17 formed in a connector 16. Connector 16 seals a valve housing 18at an extremity in a fluid-tight manner and is integrally connected tovalve housing 18, in this instance, by a sketched welding seam 19.Connector 16 has an intake bore 20, which connects blind hole 17 to afuel duct which extends inside valve housing 18, but is not shown here.The fuel duct in turn discharges into a valve chamber upstream from ametering orifice of valve 12. Pipe connection 15 is fixed in place onconnector 16 and on valve housing 18 by means of a plastic extrusioncoat 21.

To connect the valve(s) 12 to fuel distributor 11, connection means areassigned to each valve 12, which connect fuel distributor 11 and valve12 to each other in the attachment region of pipe connection 15 anddischarge orifice 14 in a pressure-tight manner. The connection meansincludes a seat surface 22 surrounding discharge orifice 14, aconnection head 23, which is integrally formed on pipe connection 15, aflange element 24, and a receiving element 25 for flange element 24.Connection head 23 has a head area 231 facing seat surface 22, and anundercut 232 facing away from head area 231. Flange element 24 engageswith undercut 232 and has at least one threaded hole 26 for a clampingbolt 27 fixed in place on fuel distributor 11. Flange element 24, whichis developed as a flat part, is accommodated in receiving element 25 andlies inside receiving element 25 in a keyed connection, threaded hole 26being correctly positioned with respect to clamping bolt 27. To achievethis, receiving element 25 has at least one bearing surface 28 forflange element 24 and a plurality of detent hooks 29 which overlapflange element 24. Each detent hook 29 has a hook strip 291 that axiallyprojects from bearing surface 28, and a detent 292 that projects in aradially inward direction from hook strip 291, which overlaps flangeelement 24 on the side facing away from bearing surface 28. Receivingelement 25 having bearing surfaces 28 and detent hooks 29 is extrudedusing plastic, concurrently with the production of plastic extrusioncoat 21 on pipe connection 15.

In the exemplary embodiment of FIGS. 1 and 2, flange element 24 isdeveloped in mirror symmetry with the valve axis and has a centralthrough hole 30 for pipe connection 15, as well as two diametricallydisposed threaded holes 26. A pressure surface 32 developed in throughhole 30 is used to place flange element 24 against undercut 232 onconnection head 23. A separate clamping bolt 27 is threaded through athrough hole 31 in fuel distributor 11 and bolted inside one of threadedholes 26 in each case. Because of the screw joint, flange element 24presses head surface 231 of connection head 23 onto seat surface 22 atdischarge orifice 14 via pressure surface 32 and undercut 232, andthereby creates a metal-to-metal seal that satisfies the high tightnessspecifications at high system pressures of the fuel by way of the highclamping forces applied by clamping bolts 27. Seat surface 22 has aconical form, and head surface 231 of connection head 23 has a sphericalform. Because flange element 24 is positioned inside receiving element25 in a keyed connection, clamping bolts 27 “blindly” find threadedholes 26 during the assembly, so that the installation process issimplified and may be carried out in an automated manner.

In the exemplary embodiment of the device shown in FIGS. 3 and 4, flangeelement 24 has been modified in comparison with the embodiment describedpreviously. The remaining components are similar to those in FIG. 1 andtherefore are designated by the same reference numerals. Flange element24, which is once again developed as a flat part, has a fork-shapeddesign and is provided with two fork arms 241, 242 which enclose pipeconnection 15, as well as a fork back 243, which interconnects fork arms241, 242. A pressure surface 321 and 322, respectively, whichcorresponds to undercut 232 on connection head 23, is formed in eachfork arm 241, 242, and threaded hole 26 for clamping bolt 27 has beenproduced in fork back 243. Receiving element 23 has three bearingsurfaces 28, for fork back 243, for the one end of fork arm 241 and forthe other end of fork arm 242, as well as three detent hooks 29, whichare embodied in the same way as in FIGS. 1 and 3. Here, too, hook strips291 of the three detent hooks 29 axially project from a bearing surface28 in each case, and detents 292, which radially project from hookstrips 291 in the inward direction overlap flange element 24 along theedge, one detent 292 overlapping fork back 243, one detent 292overlapping the end of fork arm 242, and one detent 292 overlapping theend of fork arm 241. Receiving element 25 having bearing surfaces 28 anddetent hooks 29 is extruded in one piece on pipe connection 15 duringplastic extrusion coating 21. Flange element 24 is retroactively latchedinto receiving element 23, or is inserted into the injection mold whenplastic extrusion coat 21 is produced. Pipe connection 15 is integrallyformed with connector 16, so that valve 12 including pipe connection 15is already completely assembled when plastic extrusion coat 21 isproduced.

1-9. (canceled)
 10. A device for metering a fuel in an internal combustion engine, comprising: a fuel distributor having a flow channel and at least one upstream discharge orifice connected to the flow channel; at least one valve for metering the fuel, the valve being connected to the fuel distributor and including a pipe connection for attachment to the discharge orifice; and a connection arrangement, wherein: the connection arrangement connects the fuel distributor and the valve to each other in an attachment region of the pipe connection and the discharge orifice in a pressure-tight manner, and the connection arrangement includes: a seat surface enclosing the discharge orifice, a connection head formed on the pipe connection and including a head area that comes to rest on the seat surface, an undercut, a flange element that engages with the undercut and has at least one threaded hole for a clamping bolt fixed in place on the fuel distributor, and a receiving element fixed in place at the valve, in which the flange element lies in a keyed connection, the threaded hole being positioned correctly with respect to the clamping bolt.
 11. The device as recited in claim 10, wherein the flange element is snapped into place in the receiving element.
 12. The device as recited in claim 11, wherein: the flange element is a flat part, and the receiving element includes: at least one bearing surface for the flange element, a plurality of detent hooks that overlap the flange element and have hook strips that axially project from the at least one bearing surface, and detents that radially project from the hook strips toward the inside.
 13. The device as recited in claim 12, wherein a keyed connection exists between the hook strips and the flange element, wherein the keyed connection positions the flange element.
 14. The device as recited in claim 12, wherein: the flange element has mirror symmetry with a valve axis, and the flange element includes: two diametrically disposed bearing surfaces as well as a central through hole for the pipe connection with a pressure surface which is formed in the through hole and corresponds to the undercut on the connection head, and two diametrically disposed threaded holes.
 15. The device as recited in claim 12, wherein: the flange element is has a form of a fork having two fork arms that surround the pipe connection and engage with a pressure surface at the undercut of the connection head, a fork back of the fork interconnects the fork arms and includes a machined threaded hole, the receiving element has three bearing surfaces, for the fork back and one end of the two fork arms in each case, and the receiving element includes three detent hooks, of which one detent hook in each case overlaps the fork back and an end of the two fork arms.
 16. The device as recited in claim 11, wherein the receiving element is formed by a plastic extrusion coat extruded onto the valve.
 17. The device as recited in claim 11, wherein: the seat surface has a conical form, and a head surface at the connection head has a spherical form.
 18. The device as recited in claim 17, wherein the seat surface and the head surface are made of metal. 